It was a photograph that royal fans had been longing for – and one they very nearly didn’t see.

The Prince and Princess of Wales released the much-anticipated birthday shot of their youngest son, Prince Louis, for his birthday last Tuesday.

On the surface, the close-up shot – showing the barefoot six-year-old grinning at the camera as he lies on a blanket on the grass – was a continuation of a tradition Prince William and Kate have maintained since the birth of eldest son Prince George in 2013.

The photo was said to have been taken by Kate at the family’s home on the Windsor Castle estate in the days before Louis’s birthday. Pointedly, it was said to be unedited.

The snap was posted on Kensington Palace’s social media accounts, some six weeks after the furore surrounding the Mother’s Day portrait that the princess admitted editing.

William and Kate thanked royal fans for the birthday messages they received for their youngest child.

“Happy 6th Birthday, Prince Louis! Thank you for all the kind wishes today,” the palace’s post read.

Amid the fallout from the infamous Mother’s Day photo and Kate’s continued treatment for cancer, royal watchers have reported the Waleses had decided to skip the traditional birthday portrait this year.

Only after fans piled in to wish young Louis a happy birthday did the couple change their mind.

And when they did, it went straight to Kensington Palace’s social media – abandoning Kate and William’s usual practice of releasing images for their children’s birthdays to news media under embargo a day ahead. That has traditionally meant British newspapers can publish a photo on the day of the birthday – this year, the media got its birthday shot at the end of the day.

The change is understood to be due to the unprecedented time the family is experiencing amid Kate’s ongoing illness – and the King’s enforced absence at the same time, due to his own cancer treatment.

Kate has been out of the public eye since the royal family’s traditional Christmas Day church service at Sandringham. First she had major abdominal surgery in January, and then – in a video that sent shockwaves around the world – revealed she was being treated for an unspecified cancer.

Kate admitted editing the Mother’s Day photo that caused such controversy. Image: TND

The 42-year-old princess’s absence sparked weeks of frenzied speculation online about her health. It culminated in paparazzi photos showing her in a car with her mother, Carole Middleton, and a viral video of her with William at a farm shop in Windsor.

“We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment,” Kate said in her video in mid March.

“My work has always brought me a deep sense of joy and I look forward to being back when I am able, but for now I must focus on making a full recovery.”

After the video, the Wales family disappeared from public view – reportedly taking shelter at their country estate, Anmer Hall – for the Easter break. Last week, with the three children back at school, Prince William resumed limited public duties with an outing to a food charity.

There is still no date for Kate’s return.

However, high on the agenda of royal fans will be the expectation of a similar photo for Princess Charlotte’s ninth birthday this coming Thursday. The prince and princess are expected to follow the same process as they did this week with Louis.

Less likely, but still possible, is a bonus photo to mark Kate and William’s 13th wedding anniversary on Monday. Picture-starved fans can only dream!